In this work, we design a novel, index guiding, silica core photonic quasi-crystal fiber (PQF) of 6, 8 and 10-folds for a wide range of operating wavelengths from 0.6 to 3&nbsp;μm. Further, we explore the various optical properties, namely, birefringence, dispersion, and nonlinearity for all the folds. Of all the folds, 10-fold PQF provides a low dispersion of −2.4765&nbsp;ps2&nbsp;km−1, a high nonlinearity of 22&nbsp;W−1&nbsp;km−1, admissible level of a less birefringence of 3.8&nbsp;×&nbsp;10−5 and confinement loss of 0.30446&nbsp;dB/cm at 1.06&nbsp;μm. These optical properties form the crucial requirements for the generation of few cycle laser pulses. Besides, we calculate the quality factor (Q) of the fundamental mode for all the folds and report a maximum quality factor of 0.9961 for the 10-fold PQF at 1.06&nbsp;μm wavelength.

Sivabalan S

Department of Instrumentation

School of Electrical Engineering

Vellore Campus

Ramesh Babu P

Department of Physics

School of Advanced Sciences

Senthilnathan K

Aruna Gandhi M.S

Nakkeeran K

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Infrared Physics & Technology

We design photonic quasi-crystal fibers (PQFs) of six-, eight-, ten-, and twelve-folds for determining the optimized efficiency as well as the bandwidth of second harmonic generation (SHG). We report a maximum SHG relative efficiency of 941.36 %  W−1  cm−2 for a twelve-fold PQF of 2&nbsp;μm pitch. The detailed numerical results reveal that, while the relative efficiency increases appreciably, the phase-matching bandwidth increases marginally, as and when the number of folds increases. As the primary interest of this work is to enhance the relative efficiency, we focus our analysis with a twelve-fold PQF for which the efficiency turns a maximum. In line with the practical feasibility of poling, we keep the pitch at 7&nbsp;μm and report an optimized relative efficiency and phase-matching bandwidth as 95.28 %  W−1  cm−2 and 50.51&nbsp;nm.cm, respectively.

Applied Optics

Designing photonic quasi-crystal fibers of various folds: onto optimization of efficiency and bandwidth of second harmonic generation

In this paper, we explore the possibility of using a new type of microstructured optical fiber called photonic quasi-crystal fiber (PQF) for enhancing the efficiency of second harmonic generation (SHG). We model a six-fold, index guided, silica core PQF with a relative air hole diameter ranging from 0.1–0.5. We compute the various factors related to SHG, namely, phase mismatch factor, wave-vector mismatch, coherence length, quasi-phase matching length and overlap area. Of the various factors, we focus more on the role of wave-vector mismatch and overlap area as these parameters are highly sensitive to the variations in the geometrical arrangement of air holes in the cladding. Further, these parameters are required to be as minimum as possible for enhancing the efficiency of SHG. We find that the wave-vector mismatch factor does decrease for higher values of pitch and for lower values of relative air hole diameter. However, the overlap area increases for higher values of pitch and for lower values of relative air hole diameter. Therefore, we optimize the hitherto mentioned parameters such that the wave-vector mismatch is 0.145&nbsp;μm−1 and the overlap area is 3.48&nbsp;μm2. With these values, we demonstrate a relative efficiency of 62.96%&nbsp;W−1&nbsp;cm−2 with the proposed PQF.

Optical Materials

Exploring a photonic quasi-crystal fiber for enhancing the efficiency of second harmonic generation: Modeling and analysis

We design an ytterbium-doped large pitch photonic quasi-crystal fiber (PQF) for amplifying high-energy ultrashort laser pulses. The proposed fiber exhibits unique properties such as very large mode area (4660 μm 2), less attenuation (0.42 dB/km), high overlapping factor (0.55 for the fundamental mode), and low bending loss. These properties help amplify with high-average power ultrashort pulses with less distortion and high efficiency. To meet these requirements, we design a fiber with optimum gain filtering as well as loss filtering. From the numerical simulation of the analytical model, we confirm that the large pitch PQF plays an indispensable role in amplifying high-energy ultrashort pulses. © 2012 IEEE.

Fulltext

IEEE Photonics Journal

Large Pitch Photonic Quasi-Crystal Fiber Amplifier

We propose a fiber stretcher for stretching the high-energy ultrashort pulses which require high dispersion and large mode area to secure high stretching ratio and for ensuring distortionless pulses. In this line, we suggest a novel design of photonic quasi-crystal fiber (PQF) to achieve the desired high normal group velocity dispersion (GVD) of 1000 ps2/km at 1.06 μm and inner core effective mode area as 35 μm2. These unique properties have been exploited to achieve a high stretching ratio (&gt;105) as well as less nonlinearity, which, in turn, results in a distortionless fiber stretcher for an Yb-doped high-energy ultrafast fiber laser system based on chirped pulse amplification. © 2006 IEEE.

Journal	Data powered by TypesetInfrared Physics & Technology
Publisher	Data powered by TypesetElsevier BV
ISSN	1350-4495
Open Access	0